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Discovering the causes of cancer and the means of prevention

Chernobyl Childhood Thyroid Dosimetry

DCEG investigators in the Radiation Epidemiology Branch (REB) investigators coordinated a study of thyroid cancer and other thyroid diseases in a cohort of 25,000 persons from Belarus and Ukraine who were exposed in childhood to fallout from the Chernobyl accident. Each member of this unique cohort had individual direct thyroid measurements of 131I activity in thyroid gland taken shortly after the accident. Recent efforts have been focused on improving estimated radiation doses to the thyroid from all exposure pathways and evaluating uncertainties in thyroid doses from intake of 131I, which contributes about 90% of the total thyroid dose.

Key improvements included:

  • Use of an expanded questionnaire to capture more detailed residential history and consumption of important dietary components;
  • Use of geographic region, age, and gender-specific values of thyroid masses derived from approximately 120,000 thyroid volume measurements of children obtained in Belarus and Ukraine;
  • Comprehensive reanalysis of the direct radiation thyroid measurements; and
  • Preparation of a database of meteorological and radiation measurements done during the first three months following the accident.

The average thyroid dose was 0.65 Gy (0.00035 – 42 Gy) in 13,204 persons in the Ukrainian screening cohort and an average thyroid dose of 0.68 Gy (0.0005 – 39 Gy) in 11,732 persons in the Belarusian cohort. These dose estimates were used to evaluate radiation-associated risk of thyroid cancer that incorporates estimates of uncertainty.

For more information, contact Dr. Vladimir Drozdovitch.